As processes for producing the aromatic polyester carbonate resins that have been suggested in the past, mention can be made of (a) the melt polycondensation process which involves carrying out a transesterification polycondensation reaction at elevated temperatures and a high vacuum; (b) the solution polycondensation process wherein the polycondensation reaction is carried out in an organic solvent at a low temperature; or (c) the interfacial polycondensation process wherein the polycondensation reaction is performed in a reaction medium consisting of water and a water-immiscible solvent in the presence of a basic inorganic compound.
In the case of the aforesaid processes (a) and (b), not only are the properties of the resulting resins poor, but there are also defects that are ascribable to the polymerization technique. On the other hand, the process (c) is considered to be a process of relatively great practicality. However, its drawback resides in the fact that a regular configuration of its constituent components cannot be achieved, with the consequence that difficulty is experienced in obtaining resins having satisfactory properties. While improvements in the process (c) have been proposed (see, for example, Japanese Laid-Open Patent Publication No. 25427/80), the operation is complicated in that the three steps of producing a dihydroxyterephthalic acid oligoester, chloroformating this ester and reacting the chloroformated product with a dihydric phenolic compound are required. Hence, this process cannot necessarily be regarded as being economical.